Valorization of Wheat Bran: Ferulic Acid Recovery Using Pressurized Aqueous Ethanol Solutions

The extraction of ferulic acid (FA) and other phenolic compounds from wheat bran can represent an interesting valorization step of this lignocellulosic biomass. In this work, pressurized hot water (PHW) and pressurized aqueous ethanol are used as solvents, and the amount of extracted FA in its free form and the total phenolic content of the extract have been evaluated. Total ferulic acid in the initial wheat bran was 2570.9 +/- 1.8 mu g/g of dry bran, being more than 98.5% esterified to arabinoxylans and other cell wall structures (insoluble-bound FA). Different concentrations of ethanol in water (0-20-50-80%), temperatures (130-145-160 degrees C) and extraction times (20-40-60 min) were tested. It was observed that low ethanol concentrations in the solvent, high temperatures and long extraction times favored the extraction, being the hydrolysis and not the solvolysis the reaction mechanism involved in the release of bound FA. Maximum FA extraction yield was found for pure water (PHW), 160 degrees C and 74 min of extraction that corresponds to a thermal severity factor of log (R-0) approximate to 3.7. The so obtained FA extraction yields are higher than those obtained with an enzymatic hydrolysis treatment performed for comparison. Graphic